feat(rules): adds no-if rule (#293)

Author: Matt Seccafien

README.md

@@ -117,6 +117,7 @@ installations requiring long-term consistency.
 | [no-focused-tests][] | Disallow focused tests | ![recommended][] | |
 | [no-hooks][] | Disallow setup and teardown hooks | | |
 | [no-identical-title][] | Disallow identical titles | ![recommended][] | |
+| [no-if][] | Disallow conditional logic | | |
 | [no-jasmine-globals][] | Disallow Jasmine globals | ![recommended][] | ![fixable-yellow][] |
 | [no-jest-import][] | Disallow importing `jest` | ![recommended][] | |
 | [no-mocks-import][] | Disallow manually importing from `__mocks__` | | |
@@ -165,6 +166,7 @@ https://github.com/dangreenisrael/eslint-plugin-jest-formatting
 [no-focused-tests]: docs/rules/no-focused-tests.md
 [no-hooks]: docs/rules/no-hooks.md
 [no-identical-title]: docs/rules/no-identical-title.md
+[no-if]: docs/rules/no-if.md
 [no-jasmine-globals]: docs/rules/no-jasmine-globals.md
 [no-jest-import]: docs/rules/no-jest-import.md
 [no-mocks-import]: docs/rules/no-mocks-import.md

docs/rules/no-if.md

@@ -0,0 +1,53 @@
+# Disallow conditional logic. (no-if)
+
+Conditional logic in tests is usually an indication that a test is attempting to
+cover too much, and not testing the logic it intends to. Each branch of code
+executing within an if statement will usually be better served by a test devoted
+to it.
+
+Conditionals are often used to satisfy the typescript type checker. In these
+cases, using the non-null assertion operator (!) would be best.
+
+## Rule Details
+
+This rule prevents the use of if/ else statements and conditional (ternary)
+operations in tests.
+
+The following patterns are considered warnings:
+
+```js
+it('foo', () => {
+ if ('bar') {
+ // an if statement here is invalid
+ // you are probably testing too much
+ }
+});
+
+it('foo', () => {
+ const bar = foo ? 'bar' : null;
+});
+```
+
+These patterns would not be considered warnings:
+
+```js
+it('foo', () => {
+ // only test the 'foo' case
+});
+
+it('bar', () => {
+ // test the 'bar' case separately
+});
+
+it('foo', () => {
+ function foo(bar) {
+ // nested functions are valid
+ return foo ? bar : null;
+ }
+});
+```
+
+## When Not To Use It
+
+If you do not wish to prevent the use of if statements in tests, you can safely
+disable this rule.

src/__tests__/rules.test.js

@@ -3,7 +3,7 @@ import { resolve } from 'path';
 import { rules } from '../';
 
 const ruleNames = Object.keys(rules);
-const numberOfRules = 33;
+const numberOfRules = 34;
 
 describe('rules', () => {
  it('should have a corresponding doc for each rule', () => {